1. Field of the Invention
The present invention relates to optics. More specifically, the present invention discloses an array of lenses for high-resolution imaging of a surface.
2. Description of the Prior Art
Traditionally, the lens for a one to one imaging optical scanner is a rod lens array. Please refer to FIG. 1, a perspective drawing of a prior-art rod lens array 100. The rod lens array 100 is constructed from a plurality of fiber optic rod lenses 110. Each individual fiber optic rod lens 110 is cut from a fiber optic glass strand, and its ends must be polished. The plurality of fiber optic rod lenses 110 are then arranged side by side, in a row or multiple rows with their optical axes in parallel, in a frame 120 and held in place by an adhesive layer 130. The fiber optic rod lenses 110 are typically made from GRIN (graduated index) fibers, with the refractive index of the glass carefully controlled during manufacture to have a graduated refractive index that decreases radially from the central axis to the edge.
However, this type of lens is expensive to manufacture. GRIN type fiber optic glass strands are expensive in and of themselves; cutting and polishing the strands to precise lengths to form fiber optic rod lenses 110, assembling them so that their axes are precisely parallel in the frame 120, and gluing the fiber optic rod lenses 110 are all precision steps for which entire technologies have had to be developed in order to satisfy requirements.
In addition, a major disadvantage of this type of lens is that because of the number of lenses and the difficulty in orienting them, it is not practical to shape the ends of the lenses so that they can magnify the surface that they are imaging; flat ends are used. In order to increase the imaging resolution, it is necessary to use larger numbers of smaller-diameter rod lenses 110, limiting the maximum resolution and driving up the costs as the desired resolution increases. Furthermore, suppliers for the necessary GRIN fiber optic strands are limited, and thus the base materials themselves are expensive.
Therefore there is need for an improved lens array for which materials are substantially cheaper and which is simpler to manufacture, and which can have increased resolution without substantially increasing costs.